1. Field of the Invention
This invention relates to both method and apparatus for determining the gage and/or wear of railroad track, and more particularly to such method and apparatus using optical scanning techniques in conjunction with a programmable computer for determining the gage and/or wear of rails. The method and apparatus of the invention is readily adaptable to determining the profile of railroad track rails.
2. Related Art
There are a number of techniques that have been proposed and/or used for determining the gage and/or wear of rails. The following patents are representative of such techniques.
U.S. Pat. No. 4,417,466; Measuring Method and Device for Measuring at Least One Geometrical Characteristic of the Head of the Rails of a Railway Track (Panetti), discloses both method and apparatus for measuring at least one geometrical characteristic of the transverse profile of the head of at least one rail of a railway track. A primary feature of such method and apparatus is the use of a reference base perpendicular to the axis of the track and parallel to a tangent line to the rolling surfaces of the two lines of rails. A further significant feature of the method and apparatus is the determination of the distances separating at least two longitudinal side lines of the tracing of the head of a rail from the reference base. The reference base may be represented by part of a measuring carriage rolling on the track by means of rollers resting vertically and horizontally against the two lines of rails.
U.S. Pat. No. 4,040,738; Railroad Track Profile Spacing and Alignment Apparatus (Wagner), uses railroad car-mounted optical range sensing units to measure the distance between each range sensor unit and the top and side surfaces of each rail. An optical system in each range sensor unit projects an image of a laser beam source onto the horizontal or vertical surface of a track rail to obtain an indication of the points on a projection plane intersected by the rail-reflected image or through a servo balancing system, the degree of movement of the optical systems required to maintain the reflected image approximately at a reference point on the projection plane.
U.S. Pat. No. 4,531,131; Method and Apparatus for Measuring Surface Roughness (Corbin), discloses method and apparatus limited by the spacing of a plurality of sensors at predetermined distance intervals apart from one another. Data samples from the sensors as they are moved relative to the surface being measured at fixed sample distance L are stored as measured over a region of the surface. The stored data is converted into second finite difference data over the region and the second finite difference data is converted into data representative of the space curve of the surface. The plurality of the sensors are spaced such that the response characteristic of the plurality of sensors is non-zero for all wavelengths of the surface roughness in excess of a predetermined folding wavelength.
U.S. Pat. No. 4,531,837; Method for Measuring the Transverse Profile of the Head of a Rail of a Railroad Track (Panetti), discloses method and apparatus which projects a radiation trace on the periphery of the head of a rail in a plane forming an angle with the longitudinal axis of the rail and observing the trace from several directions located outside of the plane of projection of the trace. The partial reproductions of the trace are superimposed and angularly displaced around a floating origin by an angle depending on the angles from which the trace is observed.
U.S. Pat. No. 3,562,419; Inspection Method and Apparatus for Track Alignment (Stewart et al), discloses a method and system for inspecting the condition of a railroad track using a TV camera mounted on a vehicle to tape record portions of a track to be inspected and screening the recorded TV picture to compare the results with a standard. The data recorded are the condition of the ballast rail anchors and tie plates, tie and rail, the track level and the alignment and gage. The optical means, or TV camera, is mounted on a longitudinal track travelling frame with a hairline reference either being provided in the camera optical system or the datum may be provided by a wire or wires extending longitudinally of the track.
In U.S. Pat. No. 4,173,073; Track Displacement Detecting and Measuring System (Fukazawa et al), a track displacement and measuring system uses a conventional three-point measuring method to obtain track displacement data for a unit chord length by sensors mounted on three predetermined parts of a track inspection car. The track displacement data is processed to determine the amount of track displacement over a track distance which is two or four times the unit chord length. The system uses a gyro device for detecting vertical track displacement irrespective of the track distance.
The system further includes reflecting members of stainless steel disposed at a predetermined angle with respect to the track, a laser pulse projector, a reflected pulse receiver and a signal processing circuit whereby errors of distance marks used for the recording of measured data can be readily corrected.
In U.S. Pat. No. 4,288,855; Device for measuring Deformations of the Travel Surface of the Rails of a Railway (Panetti), a travelling chassis mounts two pickups arranged opposite a line of rails at a distance apart from each other which is dependent on the length of the wavelength of the deformation to be measured. The signals from the two pickups are input to a measuring circuit with a comparator for forming the difference of the two pickup measurements. The effective wavelength of the deformations is determined and the true magnitude of the trough of the deformation is determined on the basis of the difference, the effective wavelength determined and the distance between the two pickups determined, with subsequent recording of the data.
In U.S. Pat. No. 4,181,430, Method and Apparatus for Optical Method of Measuring Rail Displacement (Shirota et al), a light projector with a slit plate, a reflection mirror for light projection, a reflection mirror for light reception, and a light receptor with a slit plate are installed at specific intervals in the longitudinal direction of the rails on a track inspection car. The light projecting and light receiving elements are arranged so that the light emitted from the light source in the light projector passes through the slit and, being reflected by the reflection mirror for light projection, is directed onto a measuring axis connecting the points as to which measurement is being made on the opposed rails which constitute the tract at at least one of the rails to form a bright spot or band of light at the measuring point on the rail. The light receptor receives only light from the rail at the measuring axis via the reflection mirror for light reception and the slit in the receptor. In the light receptor, a deviation of the points indicated by movement of the bright spot or band due to deviation of the rail position is detected during the running of the track inspection car along the track, and by comparing the deviation with the position of the reference measuring points when the rails are in the correct position, the rail displacement, the track gage deviation and misalignment can be measured.
In U.S. Pat. No. 3,864,039, Rail Gage Apparatus (Wilmarth), light sources mounted on a revenue producing train are focused onto the rail such that the rails reflect certain of the light back to the sensors mounted on the underside of the train, whereby a signal is produced indicating any shifts in the movement of the rails. The sensors comprise a photodetector having an array of photodiodes, the signal outputs of which are input to a processing unit. The projected image is a shadow or a silhouette because the railhead is opaque. As the gage of the rail changes, more or less of the photodiodes are illuminated, and since the signals from the two arrays are correlated electrically in the signal processing unit, an analog signal proportional to gage is obtained.